Performance decrease after extended period of writes and deletions

I'm using ramdisk as a temporary space to put tar files for extraction to a NAS. It works quite well to start out, but after a few writes and deletions of tar files ranging from 10GB to 25GB the performance degrades back to what the disk would be. Is it paging to disk? Considering unmounting and remounting after every tar file is processed. Thanks

Thanks for the reply. The ramdisk is handling the extraction of a large tar file from a gz file on the NAS, so it's a single file being extracted to the ramdisk. It may have to do with limited read speed from the NAS actually since it appears the write queue to the NAS for the millions of small files extracted from the previous tar has not yet filtered through.